Method and system for femtocell positioning using low earth orbit satellite signals

ABSTRACT

Methods and systems for femtocell positioning using low Earth orbit (LEO) satellite signals may comprise receiving LEO RF satellite signals utilizing a LEO satellite signal receiver path when medium Earth orbit (MEO) signals are attenuated below a threshold needed for positioning purposes. A position of said wireless communication device (WCD) may be measured based on the received LEO RF satellite signals. The measured position of the WCD may be compared to a threshold radius defined by a stored initial position. Wireless communication services to the other WCDs may be enabled when the measured position is within the threshold radius. Reentry of the stored initial position may be requested when the measured position is outside of the threshold radius. The WCD may be disabled when the measured position of the WCD falls outside of the threshold radius more than a predetermined number of times.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application is a continuation of application Ser. No. 14/589,781,which is a continuation of application Ser. No. 13/587,193 filed on Aug.16, 2012, which makes reference to and claims priority to ProvisionalApplication No. 61/569,359 filed on Dec. 12, 2011. Each of the abovestated applications is hereby incorporated herein by reference in itsentirety.

The above indicated application is hereby incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to wireless communication.More specifically, certain embodiments of the invention relate to amethod and system for femtocell positioning using low Earth orbitsatellite signals.

BACKGROUND OF THE INVENTION

Global navigation satellite systems (GNSS) such as the NAVSTAR globalpositioning system (GPS) or the Russian GLONASS provide accuratepositioning information for a user anywhere on Earth that GNSS signalsmay be received. GNSS satellites are medium earth orbit satellites,about 12,000 miles above the surface. Highly accurate GNSS clock signalsfrom these satellites may be used to accurately determine the positionof a receiver.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with the present invention as set forth inthe remainder of the present application with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

A system and/or method for femtocell positioning using low Earth orbitsatellite signals, substantially as shown in and/or described inconnection with at least one of the figures, as set forth morecompletely in the claims.

Various advantages, aspects and novel features of the present invention,as well as details of an illustrated embodiment thereof, will be morefully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a diagram of an exemplary dual mode femtocell system inaccordance with an embodiment of the invention.

FIG. 1B is a block diagram of an exemplary dual mode global navigationsatellite system in accordance with an embodiment of the invention.

FIG. 1C is a schematic illustrating failed femtocell positionverification in accordance with an embodiment of the invention.

FIG. 1D is a schematic illustrating a successful femtocell positionverification in accordance with an embodiment of the invention.

FIG. 2A is a diagram illustrating an exemplary dual mode radio frequencyreceiver, in accordance with an embodiment of the invention.

FIG. 2B is a block diagram illustrating a dual-mode time-division duplexsatellite receiver, in accordance with an embodiment of the invention.

FIG. 3 is a diagram illustrating an exemplary in-phase and quadrature RFfront end, in accordance with an embodiment of the invention.

FIG. 4 is a diagram illustrating an exemplary phase locked loop, inaccordance with an embodiment of the invention.

FIG. 5 is a diagram illustrating an exemplary intermediate frequencypath, in accordance with an embodiment of the invention.

FIG. 6 is a block diagram illustrating exemplary steps for femtocellpositioning utilizing low Earth orbit satellite signals, in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain aspects of the invention may be found in a method and system forfemtocell positioning using low Earth orbit satellite signals. Exemplaryaspects of the invention may comprise receiving an initial position of awireless communication device as entered by as user, manufacturer of thewireless device, or a service provider, wherein said wirelesscommunication device comprises a low Earth orbit (LEO) satellite signalreceiver path. The wireless communication device may be operable toprovide wireless communication services to other wireless communicationdevices. LEO RF satellite signals may be received utilizing the LEOsatellite signal receiver path and a position of the wirelesscommunication device may be measured based on the received LEO RFsatellite signals. The measured position of the wireless communicationdevice may be compared to a threshold radius defined by the initialposition and the wireless communication services to the other wirelesscommunication devices may be enabled when the measured position iswithin the threshold radius. Reentry of the initial position may berequested when the measured position is outside of the threshold radiusand the wireless communication device may be disabled when the measuredposition of the wireless communication device falls outside of thethreshold radius more than a predetermined number of times. The wirelesscommunication device may comprise a femtocell device, a WiFi accesspoint, or may provide cellular telephone service to the other wirelesscommunication devices. The position of the wireless device may bemeasured upon powering up of the wireless communication device. Theposition of the wireless device may be measured on a periodic basis. Theposition of the wireless communication device may be measured when oneor more motion sensors in the wireless communication device detectmotion. The wireless communication device may be controlled by a reducedinstruction set computing (RISC) central processing unit (CPU).

As utilized herein, “and/or” means any one or more of the items in thelist joined by “and/or”. As an example, “x and/or y” means any elementof the three-element set {(x), (y), (x, y)}. As another example, “x, y,and/or z” means any element of the seven-element set {(x), (y), (z), (x,y), (x, z), (y, z), (x, y, z)}. As utilized herein, the terms “block”and “module” refer to functions than can be implemented in hardware,software, firmware, or any combination of one or more thereof. Asutilized herein, the term “exemplary” means serving as a non-limitingexample, instance, or illustration. As utilized herein, the term “e.g.,”introduces a list of one or more non-limiting examples, instances, orillustrations.

FIG. 1A is a diagram of an exemplary dual mode femtocell system inaccordance with an embodiment of the invention. Referring to FIG. 1A,there is shown a satellite navigation system 100 comprising a pluralityof wireless communication devices 101, a building 103, medium Earthorbit (MEO) satellites 105, low Earth orbit (LEO) satellites 107, and afemtocell 109. There is also shown the approximate height in miles ofmedium Earth and low Earth satellites of ˜12,000 miles and ˜500 miles,respectively.

The wireless communication devices 101 and the femtocell 109 maycomprise any device or vehicle (e.g. smart phone) where its user maydesire to know the location of such device or vehicle. The femtocell 109may also comprise a wireless communication device, but one that isoperable to provide wireless communication services to other wirelesscommunication devices. Accordingly, the femtocell 109 may comprise aglobal navigation satellite system (GNSS) receiver having a configurableRF path that may be operable to receive medium Earth orbit (MEO)satellite signals and low Earth orbit (LEO) satellite signals. Inanother exemplary scenario, the femtocell 109 may comprise two RF pathsto receive different satellite signals.

The MEO satellites 105 may be at a height of about 12,000 miles abovethe surface of the Earth, compared to about 500 miles above the surfacefor the LEO satellites 107. Therefore, the signal strength of LEOsatellite signals is much stronger than MEO satellite signals. The LEOsatellites 107 may typically be used for telecommunication systems, suchas satellite phones, whereas the MEO satellites 105 may be utilized forlocation and navigation applications.

In certain circumstances, MEO signals, such as GPS signals, may beattenuated by buildings, such as the building 103, or other structuresto such an extent that GPS receivers cannot obtain a lock to any GPSsatellites. However, due to the stronger signal strength of LEOsatellite signals, the LEO signals may be utilized by devices tosupplement or substitute the MEO systems in the devices. However, thefrequencies utilized for MEO and LEO satellite communication are not thesame, so a conventional GPS receiver cannot process LEO signals such asIridium signals.

In an exemplary embodiment, the femtocell 109 may be operable to receiveboth LEO satellite signals, such as Iridium signals, and MEO signals,such as GPS signals. In this manner, the receiver may be able todetermine the user's location despite having high attenuation of GPSsignals to below that of the sensitivity of the receiver. Thus, thefemtocell 109 may be able to accurately determine its location byreceiving either or both Iridium and GPS satellite signals. This may beenabled by utilizing separate RF paths, one path configured to receiveMEO signals and the other path configured to receive LEO satellitesignals.

In an exemplary scenario, the two separate RF paths may share somefront-end components, such as an antenna, low-noise amplifier (LNA), anda splitter, for example. In this scenario, the shared front-endcomponents may comprise enough bandwidth to process both MEO and LEOsignals. In another exemplary scenario, the wireless device may utilizeseparate front-end components. Furthermore, in instances where only onetype of signal is to be received, the inactive RF path may be powereddown to conserve power.

In yet another exemplary scenario, the separate RF paths may betime-division duplexed (TDD), or selectively enabled, such that both MEOand LEO signals may be received, but at alternating times. This mayenable MEO-assisted LEO positioning or LEO-assisted MEO positioning, forexample. The femtocell 109 may comprise a blanking or switching modulefor enabling TDD signal reception, where the TDD process may be carriedout in the digital domain. For example, the MEO, or GPS, processing pathmay be blanked, i.e. set to and held at the last sampled value, whilethe LEO path receives and demodulates LEO signals.

In an exemplary embodiment, the femtocell 109 may comprise a dual modereceiver that may be operable to receive LEO satellite signals, such asIridium signals. In this manner, the receiver may be able to determinethe location of the femtocell 109 in the building 103 despite havinghigh attenuation of GPS signals to below that of the sensitivity of thereceiver. Thus, the femtocell 109 may be able to accurately determineits location by receiving both GPS and Iridium satellite signals. Thismay be enabled by utilizing a configurable PLL to switch to a LEOsatellite signal when MEO signals are attenuated by interveningstructures, such as when the femtocell 109 is operated inside a buildingwhere GPS signals are insignificant. The configurable receiver isdescribed further with respect to FIGS. 2A-5. Furthermore, the receivermay comprise separate RF receiver paths for MEO and LEO signals, whichmay be selected in a time division multiplexing fashion, for example.

Determining the location of a wireless device using stronger LEOsatellite signals, particularly when coarse location is acceptable, usesmuch less power than weaker MEO (e.g. GPS) satellite signals,particularly with fine location calculations. Furthermore, the receivercan vary the number of satellites used, and thus the on-time for the LEORF path, when coarse location is acceptable. Conversely, when higheraccuracy is desired, more satellites may be utilized for determininglocation.

Determining the location of femtocell devices may be useful for serviceproviders and for E911 applications, for example. A service provider mayprovide femtocell services at a particular address, such as at abusiness address in the building 103, for example, and may wish toensure that the femtocell device 109 remains at that location and is notrelocated to a location outside of the service agreement.

The femtocell 109 may comprise programmable location services, in thatit comprises GPS positioning capability and also has LEO positioningcapability for when there is insufficient GPS coverage, such as when thedevice is inside a building. In an exemplary scenario, the device mayset to automatically select GPS signals for positioning when availableand switch to LEO when necessary, or may be user selectable.

A femtocell with LEO satellite signal positioning capability enables aservice provider to monitor the location of the device, and disable thedevice when not used at the agreed location or locations. The inventionis not limited to only femtocell transceivers, and may include VoIP,set-top boxes, gateways, or other equipment where indoor positioning maybe mandated or desirable for security and/or spectrum control.

It should be noted that while a femtocell device is illustrated in thefigures, any wireless communication service may be utilized, such asWiFi, cellular, or ZigBee, for example.

FIG. 1B is a block diagram of an exemplary dual mode global navigationsatellite system in accordance with an embodiment of the invention.Referring to FIG. 1B, there is shown a global navigation satellitesystem 150 comprising the femtocell device 109, MEO satellites 105, andLEO satellites 107.

The femtocell device 109 may comprise common RF front end elements suchas an antenna/low-noise amplifier (LNA)/signal splitter 111. Thefemtocell device 109 may also comprise configurable or dual MEO/LEO RFpaths 113, a processing block 115, a femtocell RF module 117, and motionsensors 118.

The configurable or dual MEO/LEO RF paths 113 may compriseamplification, down-conversion, filtering, and analog-to-digitalconversion capability for received MEO and LEO signals. Portions of theconfigurable or dual MEO/LEO RF paths 113 may be selectively enabled ordisabled utilizing the processing block 115 to conserve power wheninsufficient signal strength is present.

The femtocell RF module 117 may comprise amplification, down-conversion,up-conversion, filtering, and analog-to-digital conversion capabilityfor communicating wireless signals in a femtocell application orproviding wireless services for wireless devices in a building or otherstructure where cellular and MEO satellite signals are attenuated. Thefemtocell RF module 117 in conjunction with the MEO/LEO positioning Rxpaths 113 enable positioning of the femtocell device 109.

The motion sensors 118 may comprise electro-mechanical devices, such asgyro-sensors, for determining when the femtocell 109 may be in motion.For example, when the femtocell is picked up, the motion sensors 118 mayindicate a vertical displacement to the processing block 115.

The processing block 115 may comprise one or more CPUs (e.g. a RISC CPU)for demodulating signals and calculating positioning information, forexample, and as such may comprise at least one positioning engine. In anexemplary scenario, the processing block 115 may comprise a MEOsatellite signal positioning engine and a LEO satellite positioningengine. Furthermore, the processing block 115 may be operable to comparethe RSSI of received LEO satellite signals to expected signal strengthsto determine when to use LEO positioning versus MEO positioning.

In an exemplary embodiment, the femtocell device 109 may compriseprogrammable location services, in that it comprises MEO and LEOpositioning capability, so that LEO signals may be utilized forpositioning when there is insufficient GPS coverage, such as when thedevice is inside a building. In an exemplary scenario, the femtocelldevice 109 may set to automatically select GPS signals for positioningwhen available and switch to LEO when necessary, or may be userselectable.

The femtocell RF module 117 may be operable to provide wireless servicesin the vicinity of the device. The positioning capability of thefemtocell device 109 enables a user or service provider to define wherethe femtocell device is authorized to operate. Accordingly, a user orservice provider may enter a location or locations where the femtocell109 is authorized to operate. In an exemplary scenario, the user mayenter the coordinates directly, or may click on a map to entercoordinates. In another exemplary scenario, the user may enter anaddress, which the femtocell or a remote server may translate tocoordinates. Upon startup, the femtocell device 109 may determine itsposition utilizing LEO and/or MEO satellite signals and enable wirelessservices when the determined position is at or near the authorizedlocations.

The femtocell may periodically check its position to ensure that thefemtocell device has not been moved to an unauthorized location. Apass/fail test may be performed on the determined position and a rangeof acceptable positions may be known from a radius surrounding theentered position. In instances where the positioning accuracy may belower, a broader acceptable range may be utilized to avoid incorrecttest failure, as described further with respect to FIGS. 1C and 1D.

FIG. 1C is a schematic illustrating failed femtocell positionverification in accordance with an embodiment of the invention.Referring to FIG. 1C, there is shown two position verifications, whichmay comprise a pass-fail criteria given a user input address translatedinto latitude, longitude coordinates, for example, and a positionmeasurement made by a LEO satellite Rx.

The position verification process may comprise several steps. First, theuser or operator enters the registered address of the femtocell into theprovider database as well as in the femtocell transceiver box, which maybe stored into non-volatile, non-tamperable memory. The entered addressmay be referred to as the initialization position, P_(init), and is notthe true position of the femtocell device in the home or business,P_(true). In another exemplary scenario, the initial position may bepre-configured, i.e., entered into the system by a manufacturer of thewireless device or by a service provider when purchased or powered upfor the first time by the user.

When the user activates the femtocell device at the home, it may boot upand perform a location measurement, P_(meas) 121A or 121B. The femtocelltransceiver may then determine if P_(meas) is within a predefined range,or accuracy threshold 119A or 119B, which may be set by the femtocellmanufacturer, or not, and apply a pass/fail criteria. If the P_(meas)fails the comparison, it is possible that this is due to a bad accuracyof the positioning performed by the receiver as shown by P_(meas) 121A.In another exemplary scenario, the true position, P_(true) 123B, mayactually be outside the boundary set by P_(init) and the accuracythreshold 119B but still result in a Pass result, even though it shouldhave failed. This may be corrected by subsequent positioningcalculations. Thus, the user may then be prompted to re-enter anestimate of the true position (i.e., reinitialize the system withP_(init)=˜P_(true)). This may be done using an Internet map tool, wherethe user points on the map where they think the box is located and thenread the latitude and longitude information. Once a new P_(init) isentered, the positioning measurement may be repeated. In instances wherethe positioning fails the accuracy threshold 119A or 119B multiplefailures, up to a predetermined maximum number, the femtocell device maybe powered down and disabled until a user contacts a service provider orother authorized entity resets the femtocell device.

Once the femtocell device is located during boot, the full system may beenabled. However, the user may move the box inside the house, to adifferent house (for example “vacation house”), or to an un-authorizedlocation (e.g. outside of the licensed spectrum). Thus, the femtocelldevice may need to perform a recheck of its location periodically, orbased on system events such as power cycling, motion detected by MEMSsensors such as a digital compass, accelerometers, or gyros. Inaddition, the femtocell transceiver may perform a position determinationon a time-basis (e.g., daily).

FIG. 1D is a schematic illustrating a successful femtocell positionverification in accordance with an embodiment of the invention.Referring to FIG. 1D, there is shown a registered location P_(init) 125Cwith the accuracy threshold 119C indicated by the circle around P_(init)125C, a measured location P_(meas) 121C, and a true location, P_(true)123C. Since the measured location, P_(meas) 121C is within the accuracythreshold 119C determined by the registered location, P_(init) 125C, theposition verification passes, and the femtocell transceiver may fullypower up with full functionality. This verification may be repeated on aperiodic basis and/or whenever the femtocell device powers up.Furthermore, gyro sensors, or other motion sensitive detectors, mayinitiate a positioning verification when motion is sensed.

FIG. 2A is a diagram illustrating an exemplary dual mode radio frequencyreceiver, in accordance with an embodiment of the invention. Referringto FIG. 2, there is shown a receiver 200 comprising an antenna 201, alow noise amplifier (LNA) 203, a signal splitter 204, a LEO path 210, aMEO path 220, a local oscillator (LO)/phase locked loop (PLL) 211, acrystal oscillator 213, a central processing unit 219, and a register221.

The LEO path 210 and MEO path 220 may comprise similar components,configured for different frequencies as needed, such as a programmablegain amplifiers (PGAs) 207A and 207B, receive signal strength indicatormodules (RSSI) 208A and 208B, mixers 209A and 209B, filters 215A and215B, and analog-to-digital converters (ADCs) 217A and 217B.

The antenna 201 may be operable to receive RF signals for subsequentprocessing by the other elements of the receiver 200. The antenna 201may comprise a single antenna with wide enough bandwidth to receive bothLEO and MEO signals, may comprise a tunable antenna to cover the desiredfrequency range, or may comprise more than one antenna for receivingsignals, each for receiving signals in one of a plurality of frequencyranges.

The LNA 203 may be operable to provide amplification to the signalsreceived by the antenna 201, with the amplified signal beingcommunicated to the splitter 204. The LNA 203 may have a wide enoughbandwidth to amplify both MEO and LEO satellite signals or may compriseparallel gain stages for LEO and MEO signals.

The signal splitter 204 may be operable to communicate part of thesignal received from the antenna 201 to the LEO path 210 and part to theMEO path 220. This may be achieved by splitting the signal at a certainpercentage to each path, such as 50%/50%, for example, or may split thereceived RF signal based on frequency, such that only MEO signals arecommunicated to the MEO path 220 and only LEO signals are communicatedto the LEO path 210. In another exemplary scenario, separate front endsmay be utilized to receive the two types of signals, i.e. a separateantenna and LNA for LEO and MEO signals that communicate the respectivesignals to the LEO path 210 and the MEO path 220.

The filters 205A and 205B may comprise active or passive filters and maybe operable to attenuate signals at frequencies outside a desired rangeand allow desired signals to pass. For example, the filter 205A may passLEO satellite signals while filtering out MEO signals.

The PGAs 207A and 207B may provide amplification to signals receivedfrom the filters 205A and 205B, and may be configured to operate at MEOor LEO frequencies, or may operate over both frequency ranges, forexample. The PGA 207 may be configured by a processor, such as the CPU219.

The filter modules 205A and 205B may comprise active and/or passivefilters for removing unwanted signals while allowing desired signals topass to the PGAs 207A and 207B. In an exemplary scenario, the filtermodules 205A and 205B comprise surface acoustic wave (SAW) filters.

The RSSI modules 208A and 208B may comprise circuitry for determiningthe magnitude of a received signal, and may sense signal strengths atthe PGAs 207A or 207B or for down-converted signals after the filters215A and 215B, for example. Accordingly, the RSSI modules 208A and 208Bmay be operable to sense signal strengths at any point along the RFpaths in the receiver 200.

The mixers 209A and 209B may comprise circuitry that is operable togenerate output signals at frequencies that are the sum and thedifference between the input RF signals and the local oscillator signalreceived from the LO/PLL 211. In an exemplary scenario, the LEO path 210and the MEO path 220 may comprise two paths each to enable the receptionof in-phase and quadrature (I and Q) signals. Accordingly, the mixers209A and 209B may each comprise two mixers, each receiving LO signalswith 90 degree phase difference to the other mixer of the pair.

In another exemplary scenario, the mixers 209A and 209B may down-convertthe received RF signals to an intermediate frequency (IF) for furtherprocessing, as opposed to down-converting directly to baseband. In thisscenario, the filter modules 215A and 215B may comprise a bandpassfilter that is configured to pass the desired IF signals while filteringout the undesired low and high frequency signals.

The LO/PLL 211 may comprise circuitry that is operable to generate RFsignals to enable down-conversion of RF signals received by the mixers209A and 209B. The LO/PLL 211 may comprise a voltage-controlledoscillator, for example, with a PLL to stabilize the frequency of theoutput signal communicated to the mixers 209A and 209B. In an exemplaryscenario, the LO/PLL 211 may generate a plurality of LO signals fordown-converting I and Q signals in the LEO path 210 and the MEO path220.

The crystal oscillator 213 may comprise a stable clock source for thereceiver 200, and may comprise a piezoelectric crystal, for example,that outputs a stable clock signal at a given temperature. The crystaloscillator 213 may comprise a source for the various LO signals to becommunicated to the mixers via the LO/PLL 211.

The ADCs 217A and 217B may comprise circuitry that is operable toconvert analog input signals to digital output signals. Accordingly, theADCs 217A and 217B may receive baseband or IF analog signals from themixers 209A and 209B and may generate digital signals to be communicatedto the CPU 219 for further processing.

The CPU 219 may comprise a processor similar to the processor 113, forexample, described with respect to FIG. 1B. Accordingly, the CPU 219 maybe operable to control the functions of the receiver 200 and may processreceived baseband or IF signals to demodulate, decode, and/or performother processing techniques to the received data. Other processingtechniques may comprise positioning calculations based on receivedsatellite signals. The CPU 219 may thus be operable to demodulate anddecode both MEO and LEO satellite data, such as GPS and Iridium data.

The CPU 219 may receive RSSI information from the RSSI modules 208A and208B and may control the gain of the various gain stages in the Rxpaths. Similarly, the CPU may control the LO/PLL 211 via the register221.

The register 221 may comprise a memory register for storing aconfiguration to be communicated to the LO/PLL to down-convert MEOand/or LEO signals. The register 221 may communicate an output signal tothe LO/PLL 211 that indicates the desired frequency signals todown-convert to received RF signals to IF or baseband.

In an exemplary scenario, the receiver 200 may be operable to receiveboth MEO and LEO satellite signals for positioning purposes. In thismanner, the wireless device that comprises the receiver 200 may becapable of determining its position even within a structure thatattenuates GPS signals.

In an exemplary scenario, 2-5 bursts from an LEO satellite may bereceived by the wireless device over a few seconds. The burst may bedown-converted and demodulated to extract an accurate clock andsatellite orbital data. These may be communicated to a position enginethat may calculate the position. Furthermore, once the satellite orbitaldata is extracted, the Doppler shift may be calculated from the burstintervals compared to the known actual burst intervals, which are knownfor each satellite.

The extracted clock may be utilized to calibrate the LO/PLL 211 and/orTCXO timing circuits 213 in the wireless communication device 101. Thismay allow the RF receive paths 210 and 220 to power down occasionally,particularly the MEO (e.g. GPS) RF path 220, since it would not beneeded to calibrate the timing circuits.

In an exemplary scenario, the LEO path 210 in the receiver 200 mayenable positioning capability even when within structures that attenuateMEO signals below a threshold needed for positioning purposes. This mayenable a femtocell device to determine its location even when GPSsignals are insufficient such that a user or service provider mayconfigure where a femtocell is authorized to operate.

FIG. 2B is a block diagram illustrating a dual-mode time-division duplexsatellite receiver, in accordance with an embodiment of the invention.Referring to FIG. 2B, there is shown an exemplary receiver 240comprising an antenna 201, a low-noise amplifier (LNA) 203, ananalog-to-digital converter (A/D) 217, a buffer 251, and two RF receivepaths, a MEO path 250, and a LEO path 260. There is also shown ablanking/switch module 259, a LO/PLL 261 and a central processing unit(CPU) 267.

The MEO path 250 may comprise a sample and hold (S/H) module 253, a GNSSacquisition module 255, and a GNSS tracking module 257. The S/H module253 may be operable to sample the digital signal from the buffer 251,and hold the sampled value for a configurable time, which may becommunicated to the GNSS acquisition module 255 and the GNSS trackingmodule 257. The S/H module 253 may thus act as a gatekeeper for data tothe GNSS acquisition module 255 and the GNSS tracking module 257. Thismay enable the receiver 250 to switch between MEO and LEO signalswithout losing a MEO value when receiving LEO signals, for example, andavoid the divergence of the output of the GNSS acquisition module 255and the GNSS tracking module 257. In another exemplary scenario, the S/Hmodule 253 may output a constant value, a string of zeroes, for example,or any known patter to avoid divergence of the output of the GNSSacquisition module 255 and the GNSS tracking module 257.

The GNSS acquisition module 255 may be operable to acquire a lock to oneor more GNSS satellites, which may allow the GNSS tracking module 257 todetermine and track the location of the receiver. The GNSS acquisitionmodule 255 may detect LEO frequency signals above a threshold signalstrength and extract an accurate clock by determining the code-divisionmultiple access (CDMA) collision avoidance (CA) code for the receiveddata. A determined satellite ID and C code may be used by the GNSStracking module 257 for accurate positioning purposes.

Similarly, the LEO path 260 may comprise a filter 263 and a LEO timingsignal demodulator module 265. The LEO timing signal demodulator module265 may receive filtered MEO signals from the filter 263 and maydemodulate the received signal to an accurate clock from thetransmitting satellite. This accurate clock along with informationregarding the satellite orbit may be utilized for positioning. In thismanner either MEO or LEO signals, or both, may be utilized forpositioning purposes.

The LEO timing demodulator 265, the GNSS acquisition module 255, and theGNSS tracking module 257 may communicate output signals to the CPU forfurther processing or use of the determined timing and/or positioningdata.

The blanking/switching module 259 may be operable to provide the TDDfunction for the receiver, switching the LEO path 260 on and off andblanking the MEO path 250 by configuring the output of the S/H module253 to retain the previous data to the GNSS acquisition module. TheLO/PLL 261 may provide a timing signal for the blanking/switch module.

The filter 263 may be operable to filter out unwanted signals allowingthe desired satellite RF signal to pass to the LEOT demodulator module265. The LEO timing demodulator may be operable to extract an accuratetiming signal from the received LEO signals, which along with satelliteephemeris data, may be utilized by the CPU 267 for positioning purposes.

In an exemplary scenario, the LEO path 260 in the receiver 240 mayenable positioning capability even when within structures that attenuateMEO signals below a threshold needed for positioning purposes. This mayenable a femtocell device to determine its location even when GPSsignals are insufficient such that a user or service provider mayconfigure where a femtocell is authorized to operate.

FIG. 3 is a diagram illustrating an exemplary in-phase and quadrature RFfront end, in accordance with an embodiment of the invention. Referringto FIG. 3, there is shown the I and Q RF path 300 comprising an antenna301, an LNA 303, a SAW filter 305, mixers 307A and 307B, filters 309Aand 309B, a 2-stage polyphase filter 311, a PGA 313, an ADC 315, adigital front end (DFE) 317, and an IF/baseband stage 319. The antenna301, the LNA 303, the SAW filter 305, the mixers 307A and 307B, thefilters 309A and 309B, the PGA 313, and the ADC 315 may be substantiallysimilar to similarly named elements described with respect to FIG. 2.

The mixers 307A and 307B may receive input signals from the SAW filter305 and local oscillator signals at frequency F_(LO), and 90 degreephase difference, to down-convert the received I and Q signals.

The 2-stage polyphase filter 311 may comprise circuitry for providing Iand Q signal image rejection of intermediate or baseband signalsreceived from the filters 309A and 309B. This has an advantage overintegrating filters prior to the mixers 307A and 307B to reduce imagesignals because this would require very high Q factors. The 2-stagepolyphase filter 311 may comprise a notch frequency of −F_(IF).

In an exemplary scenario, the ADC 315 may comprise a sigma-deltaconverter. The DFE 317 may comprise circuitry that is operable todecimate the digital signal received from the ADC 315. In an exemplaryscenario, the ADC 315 may generate a 1-bit output signal at a frequencyF_(ADC), and the DFE 317 may then decimate the received signal by 16 toresult in a 6 bit IF signal with a sampling frequency of F_(LO)/96.

The IF/baseband stage 319 may comprise circuitry for further processingof the IF or baseband signals received from the DFE 317. For example, ifthe DFE 317 output signal is an IF signal, the IF/baseband stage 319 maycomprise further down-conversion capability. In addition, theIF/baseband stage 319 may comprise filtering and decimation capabilityfor further processing of the received signals.

In operation, the I and Q RF path 300 may receive an RF signal via theantenna 301. The LNA 303 may provide amplification to the receivedsignal before being filtered by the SAW filter 305. The SAW filter 305may comprise a filter with wide enough bandwidth for both LEO and MEOsignals or may be configurable to different frequency ranges. In anotherexemplary scenario, the SAW filter 305 may comprise a plurality offilters that may be selectively enabled so that only desired signals arepassed to the mixers 307A and 307B.

The mixers 307A and 307B may receive the filtered RF signals and localoscillator signals F_(LO) that are 90 degrees out of phase fordown-converting I and Q signals to IF or baseband frequencies. Theresulting IF or baseband signals may be filtered by the filters 309A and309B and the 2-stage polyphase filter 311 before being amplified by thePGA 313. The 2-stage polyphase filter 311 may provide image rejection ininstances where image signals interfere with the desired signals. ThePGA 313 may receive a gain control signal from a processor, such as theCPU 219 described with respect to FIG. 2A.

The ADC 315 may convert the amplified and filtered IF/baseband signal toa digital signal for further processing in the digital domain. Forexample, the DFE 317 and the IF/baseband stage 319 may decimate andfilter the digital signal received from the ADC 315. In addition, theIF/baseband stage 319 may comprise a positioning engine for determiningthe location of the wireless device comprising the I and Q RF front end300. The position may be determined from accurate timing signalsreceived from a plurality of LEO or MEO satellite signals in conjunctionwith ephemeris data for the satellites.

In an exemplary scenario, the I and Q RF path 300 may receive LEOsatellite signals. The received LEO signals may enable positioningcapability even when within structures that attenuate MEO signals belowa threshold needed for positioning purposes. This may enable a femtocelldevice to determine its location even when GPS signals are insufficientsuch that a user or service provider may configure where a femtocell isauthorized to operate.

FIG. 4 is a diagram illustrating an exemplary phase locked loop, inaccordance with an embodiment of the invention. Referring to FIG. 4,there is shown a phase locked loop (PLL) 400 comprising atemperature-compensated crystal oscillator (TXCO) 401, a phase-frequencydetector (PFD) 403, a charge pump 405, a loop filter 407, avoltage-controlled oscillator (VCO) 409, divide-by-2 modules 411A and411B, a divide-by-3 module 413, a delta-sigma modulator (DSM) 415, and afractional-N divider 417. There is also shown a clock signal CLK andoutput signals F_(LO) and F_(LO)/6.

The TCXO 401 may comprise a crystal oscillator that is capable ofproviding a stable clock signal, CLK, over an operational temperaturerange. The TCXO 401 may thus provide the base clock signal for the PLL400 that is communicated to the PFD 403.

The PFD 403 may comprise circuitry that is operable to sense a phasedifference between received input signals, such as the signals receivedfrom the TCXO 401 and the fractional-N divider 417. The PFD 403 mayoutput a phase error signal, which is proportional to the phasedifference between the two input signals. This error signal may becommunicated to the charge pump 405 for adjustment purposes.

The charge pump 405 may comprise circuitry that is operable to adjust afrequency of the VCO 409 via the filter 407. The charge pump 405 mayreceive an error signal from the PFD 403 that is proportional to thephase difference between input clock signals. Accordingly, the chargepump 405 may generate an output signal that increases or decreases theoscillation frequency of the VCO 409.

The loop filter 407 may comprise a low-pass filter, for example, thatfilters out noise signals and allows a control signal to pass from thecharge pump 405 to the VCO 409. Removing spurious signals and noisefluctuations may increase the stability of the PLL 400.

The VCO 409 may comprise circuitry that is operable to generate a clocksignal at a frequency configured by an input voltage. Accordingly, thefrequency of the output signal generated by the VCO 409 may beproportional to the magnitude of the voltage of the input signalreceived from the charge pump 405 via the loop filter 407. The outputsignal may then be communicated to the divide-by-2 modules 411A and411B, which may comprise frequency dividers. The divide-by-2 module 411Amay generate an output signal F_(LO), which may correspond to theF_(LO), described with respect to FIG. 3, and may also communicate anoutput signal to the divide-by-2 module 411B for a second halving of thefrequency.

The divide-by-2 module 411B may communicate an output signal to thedivide-by-3 module 413 and the fractional-N divider 417. The divide-by-3module 413 may divide the frequency again by 3, resulting in an outputsignal F_(LO)/6. The fractional-N divider 417 may divide the frequencyof the input signal by a configurable factor, thereby enabling accuratefrequency control of the PLL 400 over a plurality of steps in afrequency range.

The fractional-N divider 417 may receive a modulus control signal fromthe DSM 415. The value of N may be configured to hop between two valuesso that the VCO 409 alternates between one locked frequency and theother. The VCO 409 may then stabilize at a frequency that is the timeaverage of the two locked frequencies. By varying the percentage of timethat the fractional-N divider 417 spends at the two divider values, thefrequency of the locked VCO 409 may be configured with very finegranularity.

In an exemplary scenario, the DSM 415 may enable the PLL 400 to hopbetween frequencies in a pseudo-random fashion to create noise shapingthat reduces the phase noise of the system. The PLL 400 may thus beoperable to provide a plurality of stable clock signals based on a TCXOoutput, and with small incremental steps in output frequency configuredby the fractional-N divider 417. The output of the divide-by-3 module413 may comprise a clock signal for the ADC 315, for example, asdescribed with respect to FIG. 3.

The configurable PLL 400 may enable the reception of LEO and MEOsignals. The reception of LEO satellite signals may enable positioningcapability even when within structures that attenuate MEO signals belowa threshold needed for positioning purposes. This may enable a femtocelldevice to determine its location even when GPS signals are insufficientsuch that a user or service provider may configure where a femtocell isauthorized to operate.

FIG. 5 is a diagram illustrating an exemplary intermediate frequencypath, in accordance with an embodiment of the invention. Referring toFIG. 5, there is shown an IF path 500 comprising a DFE 501, mixers 503Aand 503, low-pass filters 505A and 505B, a decimator 507, and a signalprocessor 506.

The IF path 500 may correspond to the DFE 317 and the IF/baseband stage319 as described with respect to FIG. 3, for example. Similarly, themixers 503A and 503B may be substantially similar to the mixers 307A and307B of FIG. 3, for example, but with different local oscillatorfrequencies. For example, the mixers 503A and 503B may receive localoscillator signals FIF, and FIF with a 90 degree phase shift,respectively, to down-convert an IF signal to baseband for furtherprocessing by the decimator 507 and the signal processor 509.

The LPFs 505A and 505B may be operable to filter out higher frequencysignals while allowing low frequency, or baseband, signals to pass. Thedecimator 507 may comprise circuitry that is operable to reduce thesampling rate of the digital input signal. For example, the decimator507 may decimate the sampling rate by a factor of 64, beforecommunicating the resulting signal to the signal processor 509.

The signal processor 509 may comprise a CPU, for example, that may beoperable to calculate positioning and navigation information fromreceived satellite signals. For example, the signal processor 509 may becomprise an assisted-GPS positioning engine that is operable tocalculate the position of the wireless device 101 from received LEO orMEO satellite signals and stored and/or retrieved ephemeris data.

By enabling the down-conversion of both MEO and LEO signals, the signalprocessor 509 may determine position and navigation information in areaswhere MEO signals are too attenuated. Similarly, the signal processor509 may alternate between MEO and LEO signal data or use data from onesignal type to assist in the positioning calculation and/or timingsynchronization of the other type of signal. The configuration of awireless device to receive both LEO and MEO signals may greatly reducespace requirements as the configurable RF path 111 may be integrated ona single chip, as opposed to multiple RF paths, each for a differentsignal type.

The reception of LEO satellite signals via the IF path 500 may enablepositioning capability even when within structures that attenuate MEOsignals below a threshold needed for positioning purposes. This mayenable a femtocell device to determine its location even when GPSsignals are insufficient such that a user or service provider mayconfigure where a femtocell is authorized to operate.

FIG. 6 is a block diagram illustrating exemplary steps for femtocellpositioning utilizing low Earth orbit satellite signals, in accordancewith an embodiment of the invention. The exemplary method illustrated inFIG. 6 may, for example, share any or all functional aspects discussedpreviously with regard to FIGS. 1-5.

Referring to FIG. 6, after start step 601, in step 603, at power up, auser enters an address or initial position, P_(init), indicating wherethe femtocell device is located. A threshold radius may be defined bythe user or a service provider within which the femtocell is authorizedto operate. In step 605, the femtocell device may determine its locationutilizing received LEO satellite signals.

If, in step 607, the measured position, P_(meas), is not within thedesired radius, the measurement may be inaccurate or an incorrectaddress may have been entered, and the exemplary steps may proceed backto step 613 where it may be determined if the position test has failedmore that X times, where X is a predetermined number of times that thepositioning test may fail before the femtocell device is disabled. Instep 613, if the positioning test has not failed more than X times, theexemplary steps may proceed back to step 603 for the user to reenter theinitial position, P_(init).

If in step 613 the positioning test has failed more than X times, theexemplary steps may proceed to step 615 where the femtocell device maybe disabled, followed by end step 619.

In step 607, if the determined position is within the threshold radius,the exemplary steps may proceed to step 617 where the femtocell devicemay finish starting up and provide wireless services, followed by endstep 619.

In an embodiment of the invention, a method and system may comprisereceiving an initial position of a wireless communication device 109 asentered by as user, manufacturer of the wireless device, or a serviceprovider, wherein the wireless communication device 109 comprises a lowEarth orbit (LEO) satellite signal receiver path 210, 260, 300, 500. Thewireless communication device 109 may be operable to provide wirelesscommunication services to other wireless communication devices 101. LEORF satellite signals may be received utilizing the LEO satellite signalreceiver path 210, 260, 300, 500 and a position of the wirelesscommunication device 109 may be measured based on the received LEO RFsatellite signals.

The measured position of the wireless communication device 109 may becompared to a threshold radius 119A-119C defined by the initial position125A-125C and the wireless communication services to the other wirelesscommunication devices 101 may be enabled when the measured position121A-121C is within the threshold radius 119A-119C. Reentry of theinitial position 125A-125C may be requested when the measured position121A-121C is outside of the threshold radius 119A-119C and the wirelesscommunication device 109 may be disabled when the measured position121A-121C of the wireless communication device 109 falls outside of thethreshold radius 119A-119C more than a predetermined number of times.

The wireless communication device 109 may comprise a femtocell device, aWiFi access point, or may provide cellular telephone service to theother wireless communication devices 101. The position of the wirelesscommunication device 109 may be measured upon powering up of thewireless communication device 109. The position of the wirelesscommunication device 109 may be measured on a periodic basis. Theposition of the wireless communication device 109 may be measured whenone or more motion sensors 118 in the wireless communication device 109detect motion. The wireless communication device 109 may be controlledby a reduced instruction set computing (RISC) central processing unit(CPU) 115, 219, 267, 509.

Other embodiments of the invention may provide a non-transitory computerreadable medium and/or storage medium, and/or a non-transitory machinereadable medium and/or storage medium, having stored thereon, a machinecode and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the steps as described herein for femtocellpositioning using low Earth orbit satellite signals.

Accordingly, aspects of the invention may be realized in hardware,software, firmware or a combination thereof. The invention may berealized in a centralized fashion in at least one computer system or ina distributed fashion where different elements are spread across severalinterconnected computer systems. Any kind of computer system or otherapparatus adapted for carrying out the methods described herein issuited. A typical combination of hardware, software and firmware may bea general-purpose computer system with a computer program that, whenbeing loaded and executed, controls the computer system such that itcarries out the methods described herein.

One embodiment of the present invention may be implemented as a boardlevel product, as a single chip, application specific integrated circuit(ASIC), or with varying levels integrated on a single chip with otherportions of the system as separate components. The degree of integrationof the system will primarily be determined by speed and costconsiderations. Because of the sophisticated nature of modernprocessors, it is possible to utilize a commercially availableprocessor, which may be implemented external to an ASIC implementationof the present system. Alternatively, if the processor is available asan ASIC core or logic block, then the commercially available processormay be implemented as part of an ASIC device with various functionsimplemented as firmware.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext may mean, for example, any expression, in any language, code ornotation, of a set of instructions intended to cause a system having aninformation processing capability to perform a particular functioneither directly or after either or both of the following: a) conversionto another language, code or notation; b) reproduction in a differentmaterial form. However, other meanings of computer program within theunderstanding of those skilled in the art are also contemplated by thepresent invention.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiments disclosed, but that the present inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method for wireless communication, the methodcomprising: in a wireless communication device comprising a low Earthorbit (LEO) satellite signal receiver path and a medium Earth orbit(MEO) path, said wireless communication device being operable to providewireless communication services to other wireless communication devices:receiving LEO RF satellite signals utilizing said LEO satellite signalreceiver path when MEO signals received by said MEO path are attenuatedbelow a threshold needed for positioning purposes; measuring a positionof said wireless communication device based on said received LEO RFsatellite signals; comparing said measured position of said wirelesscommunication device to a threshold radius defined by a stored initialposition; and enabling said wireless communication services to saidother wireless communication devices when said measured position iswithin said threshold radius.
 2. The method according to claim 1,comprising requesting reentry of said stored initial position when saidmeasured position is outside of said threshold radius.
 3. The methodaccording to claim 1, comprising disabling said wireless communicationdevice when said measured position of said wireless communication devicefalls outside of said threshold radius more than a predetermined numberof times.
 4. The method according to claim 1, wherein said wirelesscommunication device comprises one or more of: a femtocell device or awireless local area network (WLAN) access point.
 5. The method accordingto claim 1, wherein said stored initial position is entered by one of: auser, a service provider, or a manufacturer of said wirelesscommunication device.
 6. The method according to claim 1, wherein saidstored initial position is entered by one or more of: manually enteringcoordinates, clicking on a map, and entering an address.
 7. The methodaccording to claim 1, wherein said wireless communication deviceprovides cellular telephone service to said other wireless communicationdevices.
 8. The method according to claim 1, comprising measuring saidposition of said wireless communication device upon powering up of saidwireless communication device.
 9. The method according to claim 1,comprising measuring said position of said wireless device on a periodicbasis.
 10. The method according to claim 1, comprising measuring saidposition of said wireless communication device when one or more motionsensors in said wireless communication device detect motion.
 11. Themethod according to claim 1, wherein said wireless communication deviceis controlled by a reduced instruction set computing (RISC) centralprocessing unit (CPU).
 12. A system for wireless communication, thesystem comprising: one or more circuits for use in a wirelesscommunication device comprising a low Earth orbit (LEO) satellite signalreceiver path and a medium Earth orbit (MEO) path, said one or morecircuits being operable to provide wireless communication services toother wireless communication devices, and said one or more circuitsbeing operable to: receive LEO RF satellite signals utilizing said LEOsatellite signal receiver path when MEO signals received by said MEOpath are attenuated below a threshold needed for positioning purposes;measure a position of said wireless communication device based on saidreceived LEO RF satellite signals; compare said measured position ofsaid wireless communication device to a threshold radius defined by astored initial position; and enable said wireless communication servicesto said other wireless communication devices when said measured positionis within said threshold radius.
 13. The system according to claim 12,wherein said one or more circuits are operable to request reentry ofsaid stored initial position when said measured position is outside ofsaid threshold radius.
 14. The system according to claim 12, whereinsaid one or more circuits are operable to disable said wirelesscommunication device when said measured position of said wirelesscommunication.
 15. The system according to claim 12, wherein saidwireless communication device comprises one or more of: a femtocelldevice or a wireless local area network (WLAN) access point.
 16. Thesystem according to claim 12, wherein said stored initial position isentered by one of: a user, a service provider, or a manufacturer of saidwireless communication device.
 17. The system according to claim 12,wherein said stored initial position is entered by one or more of:manually entering coordinates, clicking on a map, and entering anaddress.
 18. The system according to claim 12, wherein said wirelesscommunication device provides cellular telephone service to said otherwireless communication devices.
 19. The system according to claim 12,wherein said one or more circuits are operable to measure said positionof said wireless communication device upon powering up of said wirelesscommunication device and/or on a periodic basis.
 20. The systemaccording to claim 12, wherein said one or more circuits are operable tomeasure said position of said wireless communication device when one ormore motion sensors in said wireless communication device detect motion.21. The system according to claim 12, wherein said wirelesscommunication device is controlled by a reduced instruction setcomputing (RISC) central processing unit (CPU).
 22. A system forwireless communication, the system comprising: one or more circuits foruse in a femtocell device comprising a low Earth orbit (LEO) satellitesignal receiver path and a medium Earth orbit (MEO) path, said one ormore circuits being operable to provide wireless communication servicesto other wireless communication devices, and said one or more circuitsbeing operable to: receive LEO RF satellite signals utilizing said LEOsatellite signal receiver path when MEO signals received by said MEOpath are attenuated below a threshold needed for positioning purposes;measure a position of said femtocell device based on said received LEORF satellite signals; compare said measured position of said femtocelldevice to a threshold radius defined by a stored initial position; andenable said wireless communication services to said other wirelesscommunication devices when said measured position is within saidthreshold radius.